Igniting apparatus



May 1, 1951 w, sM s 2,550,875

IGNITING APPARATUS Filed Sept. 16, 1948 [nre'nfor Patented May 1, 1951 UNITED STATES PATENT QFFICE IGNITING APPARATUS Wijtze Beye Smits, Voorburg, Netherlands, as-

signer to Smitsvonk N. V., The Hague, Netherlands 9 Claims.

The invention relates to an electric igniting apparatus which is particularly adapted for the ignition of burners operating with liquid fuel or like devices. Usually such burners are ignited by means of an igniting apparatus working at high voltage and comprising a spark plug, the electrodes of which are separated by an open gap. The ignition of such apparatus gives rise to many difiiculties. In spite of the fact that the spark plug is screened as much as possible from the jet of fuel a quantity of fuel is soon deposited into the gap between the electrodes and on the insulating parts of the spark plug, so that soon the spark plug will cease to work properly or even cease to produce sparks. Besides the ignition becomes more diilicult and unreliable as the quantity of air supplied to the burner is increased. Deposition of soot due to the combustion may put the spark plug entirely out of opera tion. Finally the normal spark plug having a gap and operating at high voltages produces a spark only very locally, viz. within the gap, so that it entirely depends on the nature of the mixture in the direct vicinity of the spark plug whether or not ignition takes place.

The invention has for its object to overcome the above mentioned difiiculties by the use of an igniting apparatus comprising a creeping spark sparking plug, to be actuated by a condenser system. Such an igniting apparatus operates, as is well known, at considerably lower voltages and works better if the distance between the electrodes on the active surface of the spark plug is bridged by a deposition of fuel or soot. The spark plug of the invention, therefore, has, on its active surface, a chamber or recess which is open to the outside and is meant for the accumulation of fuel, e. g. mineral oil. The electrodes of this spark plug are connected with a condenser system by means of a certain contact apparatus and circuit connections which, when the burner is to be ignited and the starting switch, a make and break switch, such as a push-button, is actuated, cause the production of at least two sparks in rapid succession on the surface of the spark plug.

in this apparatus fuel is brought into or col lected the open recess of the spark plug. This fuel is blown out of that recess with great force by the first spark and the cloud of atomized fuel is ignited the next spark or sparks. Thereby a big flame is produced which ignites the fuel injected into the burner. This way of ignition appears to be simulated by the dirtiness of the spark plug caused by fuel deposited on or in the spark plug and it further appears to be insensible to the pressure and the velocity of the mixture to be ignited. Without any difiiculty to the ignition the quantities of injected fuel and supplied air may be increased to the highest practical degree.

The shape of the cloud sprayed from the recess of the spark plug depends on the shape of said recess and that of its opening to the outside.'

When these shapes are chosen well the cloud of fuel atomized by the first spark can be adapted to the exigences of the burner.

According to an embodiment of the inventiontwo sparks may be produced by one and the same condenser. serted by means of the contacting device first into the charging circuit and directly after that into the discharging circuit of the said condenser. This apparatus is simple but produces sparks of equal energies.

It is also possible to use two or more different condensers which are connected to the spark plug in rapid succession by the contacting device; If the condensers have different capacities sparks of difierent energies are obtained.

Preferably, the contacting device is provided with means by which the switching velocity of said device can be regulated. The time interval between the spark for the atomizing and the spark or sparks for the ignition can be adjusted then.

The invention also includes a liquid burner provided with an igniting apparatus of the above described kind.

For further illustration of the invention reference is made to the accompanying drawing in which:

Fig. 1 is an electrical diagram of anigniting Fig. 3 is a longitudinal sectional view of a spark plug for an igniting apparatus as shown in Fig. 1 or 2, and

Figs. 4, 5, 6 and 7 show different shapes of the active parts of the spark plug.

In Fig. 1 of the drawing i is a push button for the control of the igniting apparatus, 2 is a bat tery, 3 is the coil of an electromagnetic relay, 6 is the armature of said relay, 5 is a piston coupled with said armature, 5 is a cylinder in which said piston is provided and 'l is an opening in the wallof said cylinder, said opening having an adjustable cross area. The relay actuates a throw-over contacting arm 3 which cooperates with fixed In that case the spark plug is incomprising three separate igniting contacts 9, 9 and Hi. The contacting arm 8 is permanently connected to one plate of an ignit ing condenser i i, the other plate of which is connected to earth through the sparking path between the electrodes of a spark plug it. The fixed contacts 9 and 9 are also connected to earth. Between fixed contact iii and earth a supplying or feeding condenser i3 is inserted, which is charged by the secondary winding is oi a transformer through a rectifier She primary winding it of the transformer is connected to the battery 2 through an electromagnetic selfinterrupter it, l8, l9 and the pushbuttcn i. The contacts I8, IQ of the self-interrupter are shunted by a condenser 24) which prevents said contacts from sparking.

When push-button l is pushed primary winding it of the transformer is, owing to the peration of the self-interrupter ll, 58, is supplied with pulsating direct current. Thereby a high alternating tension of about 1500-2G09 volts is generated in secondary winding it, said tension being fed to supplying condenser l3 through rectifier l5, so that said condenser is loaded.

At the same time coil of the relay is supplied with current from battery 2 and armature d is attracted. The movement of armature #3 and that of contacting arm 8 connected thereto are delayed by the damping device 5, 5, 1. Contacting arm 8 now contacts first fixed contact is and thereupon the earthed contact e'. Since supplying condenser !3 has a much larger capacity than igniting condenser H, the latter will, during the passage of contact ill by contacting arm 8, be suddenly loaded through spark plug l2 and, when said arm touches fixed contact 9', be discharged through said spark plug just as rapidly. This igniting device produces two sparks of equal energies in rapid succession. The speed of succession of said sparks is defined by the adjustment of the damping device 5, 6, 1. When the push-button is released relay 3, t becomes dead and contacting arm 8 returns to the original position. Since supplying condenser is is then still charged two sparks will again be produced at the spark plug.

If a number of igniting sparks of different energies are required an igniting apparatus according to Fig. 2 may be used. In this apparatus three igniting condensers are provided and relay 3, 4 controls three contacting arms 8a, 8b, and 80 which cooperate with fixed contacts 9a, 9b, 9c, S'a, 9b, 9c, 9"a, 9"19, 9"0, Ella, ml), lic respectively. This apparatus operates in the same way as that shown in Fig. l as far as the loading of supplying condenser 63' and the feeding of relay 3, 4 are concerned. When relay 4, 3 is fed contacting arms to, 8b and 8c are brought in the positions Ida, [0b and Hie after having passed all contacts 9. In these positions igniting condensers Ila, Nb and Ho are charged from the load of supplying condenser l3.

When push-button l is released contacting arms 8a, 8b, 80 return to their original positions. During said return movement first condenser I la is discharged through contact 9a and spark plug l2, then condenser lib is discharged through contact 9'1) and said spark plug and finally condenser Hc is discharged through contact 9"0 and the spark plug.

Thus in this igniting apparatus three sparks are produced in rapid succession. The spacing in time of the sparks can be regulated by the damping device 5, 6, 7. When the capacities of 4 condensers Ila, lib, Hc are different the energies of the three sparks will be different.

Fig. 3 illustrates a spark plug which can be used in an igniting apparatus as shown in Figs. 1 and 2. This spark plug is provided with an annular outer electrode 2!, a central electrode 22 and an insulating or semi-conductive separating member 23 interposed between said electrodes. The spark is produced as a creeping spark which creeps over the top surface of the separating member 23. The central electrode 22 and the separating member 23 terminate some distance below the top surface of the annular electrode 2|, so that a chamber or recess 26 is formed. In this recess fuel is collected, which is injected in the combustion chamber of the burner or like apparatus. Said fuel is blown energetically out of recess 2 by the first spark and is atomized to form a cloud. Said cloud of atomized fuel is ignited by the next spark or sparks so that a flame is obtained which ignites the burner or the like.

In Fig. l recess 24a of the spark plug has the shape of a hyp-erboloid; in Fig. 5 the recess 2% is spherical; in Figs. 6 and 7 the recesses 24c and 2M are shaped as truncated cones.

What I claim is:

1. A switch controlled electrical igniting apparatus particularly for oil burners comprising a surface discharge spark plug having a recess open. to one side and disposed so as to be accessible to oil from the jet of sa d burner and to receive oil therefrom and sparking electrodes electrically separated by a member forming together with said electrodes a part of the wall of said recess, a multiple step switch comprising a row of stationary contacts and a movable contact, means for moving said movable contact over said row of stationary contacts, a device for generating a direct current, a feeding condenser permanently connected across and loaded by said current generating device, said feeding condenser being connected, with one plate, to at least one stationary contact of said switch and, with the other plate, to both at least one other stationary contact of the switch and one electrode of the spark plug and an igniting condenser, of which one plate is connected to the movable contact of said switch and the other plate is connected to the other electrode of said spark plug, said igniting condenser being, when said movable contact is moved over said row of stationary contacts, successively at least one time charged and one time discharged through said spark plug, thereby causing at least twice sparking of said spark p ug.

2. In a switch controlled electrical igniting apparatus accord ng to claim 1 the means for operating the movable contact of the switch beng an electro-magnet comprising an exciter coil. and a movable armature mechanically coupled with said movable contact and the provision of a source of electricity and a starting make and break switch connected in series with said coil across said source of electricity.

3. In a switch controlled electrical igniting apparatus according to claim 1, the means for operating the movable contact of the switch being an electromagnet comprising an exciter coil and a movable armature mechanically coupled with. said movable contact, the provision of a source of electricity and a starting make and break switch connected in series with said coil across said source of electricity and the provision of regulable action retarding means connected to said movable armature.

4. In a switch controlled electrical igniting apparatus according to claim 1, the means for operating the movable contact of the switch being an electromagnet comprising an exciter coil and a movable armature mechanically coupled with said movable contact, the provision of a source of electricity and a starting make and break switch connected in series with said source and both the coil of said electromagnet and the direct current generating device for loading the feeding condenser being connected across the series connection of said source and said starting switch.

5. A switch controlled electrical igniting apparatus particularly for oil burners comprising a surface discharge spark plug having a recess open to one side and disposed so as to be accessible to oil from the jet of said burner and to receive oil therefrom and sparking electrodes electrically separated by a member forming together with said electrodes a part of the wall of said recess, at least two multiple step switches each comprising a row of stationary contacts and a movable contact, means for moving the mechanically interconnected movable contacts over the corresponding rows of stationary contacts, a device for generating a direct current, a feeding condenser permanently connected across and loaded by said current generating device, said feeding condenser being connected, with one plate, to one stationary contact of each step switch and, with the other plate, to one electrode of the spark plug, the other electrode of the spark plug being connected to another stationary contact of each step switch and at least two igniting condensers, each of which is connected, with one plate, to the movable contact of a step switch, and, with the other plate, to the interconnection of the feeding condenser and the spark plug, said igniting condensers being loaded by said feeding condenser when the movable contacts of said switches are in their starting position and successively discharged through said spark plug when the movable contacts of said switches are moved over the corresponding rows of stationary contacts, thereby causing at least twice sparking of said spark plug.

6. In a switch controlled electrical igniting apparatus according to claim 5, the provision of igniting condensers of different capacities.

7. In a switch controlled electrical igniting apparatus according to claim 5, the means for operating the movable contacts of the multiple step switches being an electromagnet comprising an exciter coil and a movable armature mechanically coupled with all movable contacts and the provision of a source of electricity and a starting make and break switch connected in series with said coil across said source of electricity.

8. In a switch controlled electrical igniting apparatus according to claim 5, the means for operating the movable contacts of the switches being an electromagnet comprising an exciter coil and a movable armature mechanically coupled with all movable contacts, the provision of a source of electricity and a starting make and break switch connected in series with said coil across said source of electricity and the provision of regulable action retarding means connected to said movable armature.

9. In a switch controlled electrical igniting apparatus according to claim 5 the means for operating the movable contacts of the switches being an electromagnet comprising an exciter coil and a movable armature mechanically coupled with all movable contacts, the provision of a source of electricity and a starting make and. break switch connected in series with said source and both the coil of said electromagnet and the direct current generating device for loading the feeding condenser being connected across the series connection of said source and said starting switch.

WIJTZE BEYE SMITS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,129,472 Lysholm Sept. 6, 1938 FOREIGN PATENTS Number Country Date 345,676 Italy Jan. 13, 1937 227,000 Switzerland Aug. 21, 1943 

